Vacuum line closure method and device for separation chambers in ground-water pumping systems



March 11, 1969 E. J. MOORE 3,431,708

' VACUUM LINE CLOSURE METHOD AND DEVICE FOR SEPARATION CHAMBERS INGROUND-WATER PUMPING SYSTEMS Filed April 25, 1967 Sheet Of 5 s 11:::IIIIIIlIfIIIITFFIrfA Q w 9 v I v r h INVENTOR fizz 42.0 /%a/PE QuLZiA77 A (W I A r zsRNE March 11, 1969 E. J. MOORE VACUUM LINE CLOSUREMETHOD AND DEVICE FOR SEPARATION CHAMBERS IN GROUND-WATER PUMPINGSYSTEMS Filed April 25, 1967 INVE TOR. [Zn 4R0 /00/PE March 11, 1969 J,MQQRE 3,431,708

VACUUM LINE CLOSURE METHOD AND DEVICE FOR SEPARATION CHAMBERS INGROUND-WATER PUMPING SYSTEMS Filed April 25, 1967 Sheet 3 of :5

wef 720M W ATTONEY United States Patent 'Oflice 3,431,708 Patented Mar.11, 1969 ABSTRACT OF THE DISCLOSURE A gas vacuum pump is connected tothe second of two series connected gas-liquid separation chambers. Theconnection to the vacuum pump is closed by a float valve whosedimensions and weight are set so that the valve closes when the Waterlevel in the chamber rises above a predetermined danger level, and openswhen the gas pressure in the chamber increases at a relatively low rateand the Water level recedes to a safe level. However, when the gaspressure level in the chamber increases at a relatively high rate, thusindicating a major malfunction in the pumping system, the valve will notre-open until it is manually actuated, even if the water drops to. asafe level.

ments for use in the gas separation apparatus forming a part of thepumping unit.

i A major problem found in the use of prior well-point equipment iscaused by the fact that the Water pumped by the system usually containsrather substantial quantities of air or other gases, and often containssubstantial quantities of sand and other foreign particles. The liquidpump in the pumping unit of a well-point system usually is a centrifugalpump. Such pumps suffer a great loss of efliciency when there is anysubstantial quantity of gas in the liquid being pumped. Hence, in mostwell-point installations, it is necessary to remove the gas from theliquid in order for the pump to operate at a relatively high efficiencyor, in some cases, in order for the pump to operate at all. 4

One device used to remove gases from the liquid is a separation chamberand vacuum pump. The usual separation chamber is a vertical tank whosebottom opens directly into the top of the pipe-line leading into thecen-' trifugal pump. A vacuum pump is connected to the top of thechamber to evacuate gas separated from the liquid.

A very long-standing problem with such a separation system is caused bythe fact that the liquid in the separation chamber bubbles violently andsplashes upwardly with great turbulence as the gas is separated from it,and tends to get into the vacuum pump. Although reciprocating vacuumpumps are not seriously affected by the liquid it is desired to userotary vacuum pumps because of their considerably better performance ata lower cost. However, rotary vacuum pumps can be damaged or ruined ifliquid from the well-points is allowed to get into them, especially ifthe liquid is ground water which carries particles of sand or otherforeign matter.

Various systems have been proposed for preventing water carry-over intovacuum pumps. However, such systems, generally have been unsatisfactory.Accordingly, it is an object of the present invention to provideapparatus for continuously removing dispersed liquids from the ground inwhich gases are removed from the liquid by means of a separation chamberand a vacuum pump without the liquid being carried into the vacuum pump.It is a further object to provide a valve arrangement for use in the gasseparation chamber of such apparatus to further insure againstcarry-over of liquid into the vacuum pump. It is another object of thepresent invention to provide apparatus having the foregoing beneficialfeatures, and which is simple in operation, requires an absolute minimumof maintenance, is relatively free from malfunction, and is compact andrelatively lightweight so as to be easily portable from one constructionsite to another. The invention now will he described with reference tothe drawings, in which:

FIGURE 1 is a perspective view of a well-point system constructed inaccordance with the present invention;

FIGURE 2 is a schematic diagram of the system shown in FIGURE 1;

FIGURE 3 is a partially broken-away and partially cross-sectional viewtaken along line 3-3 of FIGURE 1;

FIGURE 4 is a cross-sectional view taken along line 4-4 of FIGURE 3 andFIGURE 5 is a cross-sectional view of a component of an alternativeembodiment of the present invention.

FIGURE 1 shows a well-point water removal system constructed inaccordance with the present invention. The system includes severalwell-points, each comprising a pipe 10 and an inlet screen 12 sunk intothe ground 14 at spaced intervals. Each well-point is connected to themain pipe 16 on the surace of the ground. The main pipe 16 is connectedto a mobile pumping unit 18 which pumps the liquid through the pipe 16from the well-points and discharges the liquid from an outlet pipe 20.As is well known, such a well-point system can be used to dry the groundto a certain depth so as to make it easier to dig excavations in it, orto draw water from the ground for industrial or domestic use, or forother well known uses.

The mobile pumping unit 18 includes a frame 22 mounted on wheels 24 oron skids (not shown). A motor or engine 26 drives a rotary pump 28through a drive shaft 30. The pump 28 pumps liquid through a dischargecheck the pipe 16 connected to it.

Rotary pump 28, which preferably is of the centrifugal type, will notoperate .at peak efficiency if the liquid being pumped has substantialquantities of gas in it. Therefore, as is shown most clearly in FIGURE2, a vertical separating chamber 40 is connected to the top of conduit38 with the conduit 38 having a hole in its top communicating with theopen bottom of chamber 40 so that gases will .tend to rise from theliquid in the horizontal conduit 38 into the chamber 40.

In accordance with the present invention, an isolation chamber 44 isprovided and connected to the top of chamber 40 by means of a gasconduit 42 of relatively large diameter. A rotary vane type of vacuumpump 48 is connected to the top of isolation chamber 44 by means ofanother gas conduit 46, also of relatively large diamterial are likelyto mar the internal components of the pump and ruin it, causing muchlost time and expense in repair or replacement of the pump.

As is shown in FIGURE 2 the gas bubbles 50 rising in the separationchamber 40 often cause turbulent agitation and upward splashes 52 of thewater in the tank 40. A conventional flap or peel valve 54 is providedat the opening to the outlet pipe 42 at the top of the chamber 40. Valve54 is operated by a float 56 in order to block the exit opening ofchamber 40 when the water level in the chamber rises too high. The valveopens and closes very rapidly so as to react quickly to the rapidfluctuations of the liquid level in the separation chamber, and to passas much gas and as little liquid as possible. However, the valve 54 doesnot prevent all of the water from splashing into the outlet pipe 42. Asa result, drops of water 58, usually numerous enough to form smallstreams, flow almost continuously through the pipe 42 into the isolationchamber 44 where no turbulence occurs and separation is complete. Undercertain conditions, the water in tank 40 will rise up to the top of thetank and great amounts of water will flow through the pipe 42 into theisolation chamber 44. Neither the small streams nor the completeoverflow of water can be tolerated by the vacuum pump 48.

In accordance with the present invention, the isolation chamber preventswater from splashing into the vacuum pump. Because there is no upwardmovement of air through the liquid in chamber 44, there is no turbulenceor splashing of the liquid in chamber 44. As a result, the vacuum pump48 receives virtually no water or solids and therefore can operate forvery long periods of time at or near maximum efiiciency. There are nobafiles in the gas flow passages to reduce the efiiciency of the pump48. In fact, the diameters of the conduits 42 and 46 can be madepractically as large as necessary to permit the full flow of gas to thevacuum pump at its rated capacity, and can be made at least as large asthe inlet opening to the vacuum pump 48.

A flap valve 60 and float 62 are provided as a safety feature to preventwater carry-over into the vacuum pump if the water level reaches the topof the isolation chamber 44 due to major malfunction of the system.

The removal of the accumulated liquid 64 from the isolation chamber 44creates special problems. The chamber 44 cannot simply be opened at itsbottom to let the water run out because the water is under a vacuum andwill not run out. Removal of the accumulated liquid is accomplished inaccordance with the present invention automatically and without the needfor another pump by providing an open return conduit 66 connected at oneend to the bottom of chamber 44, and at its other end 68 into the bottomof the inlet conduit 38 at which point the liquid from chamber 44 flowsinto the liquid in the conduit 38 from which a substantial portion ofthe gas has escaped. Under normal conditions, the pressure at the returnconduit outlet 68 usually is somewhat greater than that in the upperpart of the isolation chamber 44. For example, the vacuum (negativepressure) at the end 68 of the return conduit might be from 9 to 29inches of mercury, and typically is around 25 inches of mercury.Typically, the vacuum at the top of chamber 44 is around 26 inches ofmercury. The isolation chamber 44 is made tall enough so that the staticpressure of the accumulated liquid 64 in the chamber will overcome anyexcess pressure at point 68 and cause the liquid 64 to dischargeautomatically from chamber 44 prior to the point where the level of theliquid 64 rises to the entrance of the vacuum pump feed line 46 at thetop of the chamber. Thus, the accumulated liquid is removed from chamber44 automatically and without a separate pump.

In an alternative embodiment of the invention, additional suction can beapplied to the return line 66 to aid in removal of accumulated liquidfrom the isolation tank 44. Accordingly, another conduit 70 (shown indashed lines in FIGURE 2) is connected at one end to the highpressureoutlet of the centrifugalwater pump 28, and at the other end forms a jetnozzle 72 which extends into the return tube outlet 68 as is shown inFIGURE 2. By means of conduit 70, a high-velocity jet of liquid isforced through the tubular end 68 of the return tube 66 so as to providecontinuous pumping action to aid in removing liquid 64 from the chamber44.

Regardless of which of the above-described emptying arrangements isused, the provision of the isolating chamber 44 solves the verylong-standing problem of liquid carry-over into the vacuum pump in awell-point system without occluding the gas flow passages. Since theliquid in the isolation chamber 44 is calm, water is not splashed intothe vacuum feed line 46. The emptying of accumulated liquid from chamber44 is automatic and is accomplished without the use of a separate pump.Furthermore, the automatic emptying arrangement is simple and relativelyfool-proof. The exit end 68 of return line 66 is located at or near thebottom of conduit 38 so as to prevent air which accumulates near the topportion of the conduit 38 from entering the return line and causing anyturbulence in the liquid 64 in isolation chamber 44. The vacuum pump 48operates near peak efficiency because of the prevention of liquidcarry-over into the pump. As a result, the centrifugal liquid pump 28operates near peak efficiency because the gases are continuously removedfrom the liquid with high efficiency. This is true despite the constantviolent turbulence in the separation tank 40, and even sudden inrush ofgreat quantities of gas into the system which frequently occurs when oneof the well-point pipes 10 is broken. Also, since none of the liquidgets into the vacuum pump, very dirty water can be pumped without fearof damaging the vacuum pump.

As is shown in FIGURE 1, the separation chamber 40 and isolation chamber44 are enclosed in an insulated housing 74 which is shown broken-away inFIGURE 1 to exposed the chambers 40 and 44 to view. Also, an outlet pipe76 is connected to the separation chamber 40. This pipe usually isplugged and is not used. However, it can be connected by means of a hoseto a pipe 78 on the top of the smoothing manifold 34, if desired.Manifold 34 is substantially similar in operation to the separationchamber 40. It may be used, if desired, to initially remove some of thegas from the liquid and smooth the flow of the liquid before reachingthe separation chamber 40.

Superficially similar ideas have been proposed for use in differenttypes of pumping arrangements, as is shown, for example in US. Patents2,275,500; 2,275,501 and 2,275,502 to Broadhurst. However, such priorart arrangements are inoperative and impractical for use in well-pointsystems.

Now referring to FIGURES 3 and 4, the construction of the separationchamber 40 is virtually identical to that of the isolation chamber 44.Each chamber includes a vertical cylinder 82, and a top plate '84. Thecylinder 82 is secured to the top plate by means of a plurality of bolts86.

The bottom of cylinder 82 for the separating chamber 40 is welded ontoan upstanding neck-portion 88 of conduit 38 which connects the bottom ofchamber 40 into the conduit 38. The diameter of the chamber 40 is onlyslightly less than that of conduit 38, thus providing a large area forthe escape of gas into the chamber 40 from the liquid. As is shown inFIGURES 2 and 4, the conduit portion 38 is of larger diameter than thepipe 16, and its centerline is located below that of pipe 16. The largerdiameter of conduit 38 slows down the liquid flow, decreases itsturbulence, and improves separation.

The bottom of chamber 44 is welded onto a bracket 90 which is weldedonto the outside of conduit 38 so as to support the isolation chamber44. The return conduit 66, which is either a metal pipe or a hose, isconnected between a hole in the bottom of chamber 44 and the pipe 66 bymeans of a conventional elbow fitting 92. Fitting 68 also is aconventional elbow fitting which is positioned at the bottom of conduit16 so as to prevent air from flowing up into the return line 66. Acheck-valve 67 is positioned in the return line 66 in order to preventair from flowing into the chamber 44 through line 66 if massiveturbulence causes air bubbles to be located temporarily at the bottom ofthe conduit 16. The outlet of fitting 68 opens towards the centrifugalpump 28 and thus tends to gain the benefit of slight suction at itsopening produced by the liquid flow past it.

FIGURE 4 shows the optional ejector emptying arrangement which also isshown in FIGURE 2. A T- shaped pipe fitting 80 is fastened to the end ofreturn conduit 66. The jetting tip 72 is fitted into one end of theT-fitting. The conduit 70 passes through the bottom of the pipe 16 andis connected to the high-pressure outlet of the pump 28.

Referring again to FIGURE 3, the top plate 84 of each chamber 40 and 44has a grid formed by a number of holes 94 in its center. These holesserve as the gas outlet openings for each chamber and are made as largeas possible while still providing a seat for the flaps of the valves 54and 60. Conventional pipe fittings 96, 38 and 100 are provided toconnect the holes 94 of chamber '44 to the vacuum pump inlet conduit 46.Furthermore, conventional fittings 102, 104, 106 and 108 are used toconnect the conduit 42 between the holes 94 in separation chamber 40 andthe inlet opening 110 in chamber 44. The latter opening is located aboutone-third of the way down from the top of chamber 44. I

The valves 54 and 60 and floats 56 and 62 are identical in bothchambers. The construction of each is wellknown. Each valve includes aflexible flap portion 112 and a relatively stiff resilient member 114which tends to press the flap 112 upwardly to close the holes 94. Thefloats 56 and 62 are joined to the flaps 112 by means of a pair ofrubber rings 116 and 118. As is well known, as each ball 56 or 62 rises,the flap 112 moves upwardly to close the openings 94. When the balldrops, the flap 112 is peeled away from its valve seat, the valve thusbeing relatively easy to open. The peel valves provide protection onlyagainst the flow of relatively large amounts of liquid out of therespective gas outlets of the chambers 40 and 44. However, they do notexcessively constrict the flow of air from the chambers because theyhave openings large enough to easily pass the full flow of gases to thevacuum pump, and because they open so quickly.

FIGURE 5 shows an alternative valve arrangement for the isolationchamber 44. The valve arrangement generally indicated 122 in FIGURE 5 isnot a flap valve as in the abovedescribed embodiment of the invention,but instead has a solid, comically-shaped metal valve member 124 whichmoves upwardly to seat itself in a frustro-conical valve seat 128 in avalve seat body 126. The valve member 124 is secured to the uppermostend of a rod 130. Secured to the lower end of the rod 130 are two hollowmetal float spheres 132 and 134. The spheres 132 and 134 are securedtogether and to the rod 130 by means of lock nuts 136 and cotter pins138. The rod 130 passes through a central hole in a weight 140. The rod130 also passes through a centrally-located hole in a U-shaped guidebracket 142 which is bolted to the upper plate 84 of the isolationchamber 44.

The isolation chamber arrangement shown in FIGURE 5 is the same as thatshown in the previous figures of the drawings except that its drainopening is centrally located in the bottom of the chamber and the drainconduit 66 is a flexible hose secured to a pipe fitting 144 which isscrewed into a fitting at the bottom of the isolation chamber. Also, anair vent valve 146 is provided in the gas conduit 46. The valve 146 canbe opened to allow air to enter the conduit 46 from the atmosphere.

The valve arrangement 122 operates as follows: When the water in chamber44 reaches a certain pre-determined level such as that indicated by thedashed line 148, for example, there is a considerably increased dangerof splashing liquid into the vacuum line, and it is desired to securelyclose the opening to the vacuum line 46 in order to insure that noliquid enters the vacuum line. The

' valve 122 closes tightly by means of a solid valve member and a solidvalve seat, an arrangement which virtually eliminates leakage. The valveseat body 126 is made of a TFE fluorocarbon material such as Teflon,sold by Du Pont, in order to provide an acid-resistant, long-wearingtight-sealing valve seat. The downward forces on the valve member due tothe weight of the valve components 124, 130, 132, 134 and are balancedagainst the upward buoyancy forces provided by the hollow spheres 132and 134 so that the valve 122 closes when the water level reaches thepre-determined danger level 148.

It will be recalled that the vacuum pump 48 is connected to the end ofvacuum line 46 as is shown in FIG- URE 2. Thus, as soon as the valve 122closes, the pressure in the vacuum line almost immediately drops to thelowest pressure that the pump 48 is capable of providing. For example,substantially immediately after the closing of the valve 122, the vacuumin the line 146 typically will increase from around 26 inches of mercuryto around 30 inches of mercury. Simultaneously, the gas pressure in thechamber 44 starts to rise; that is, the vacuum decreases. The reason forthis is that gas continues to separate out from the liquid being pumped.This gas collects in the chambers 40 and 44. Since gas is not beingremoved from the chambers due to the fact that the vacuum line 46 isclosed, the pressure in chamber 44 increases. Thus, there is created acorresponding upward force on the valve member 124 due to the pressuredifference between its upper and lower surfaces. What is more, thispressure difference almost always is substantial, e.g., 3 to 5 inches ofmercury almost immediately after closing of the valve. In accordance'with the present invention, this pressure differential is used to holdthe valve tightly shut for a substantial length of time after the waterlevel in chamber 44 has receded below the danger level 148. The waterdrains from chamber 44 at a relatively slow rate. For example, itnormally takes about 7 seconds to drain all of the water from the dangerlevel 148. When the system is operating normally, after the water levelhas dropped almost to the bottom of the lowest globe 134, the weight ofthe valve components exceeds the total upward forces created by thepressure differential and the buoyancy of the floats, and the valvemember 124 falls away from the valve seat 128 and comes to rest againstthe bracket 142. This opens the vacuum line so that normal removal ofgases from the chambers 40 and 44 is resumed.

If the pumping system is operating normally, the rate of pressure risein the chamber is gradual, e. g., about one inch of mercury per second.However, if there is a major malfunction in the system, such as whereone of the well-points 10 accidentally has been broken off and greatquantities of air are being drawn into the liquid, the pressure inchamber 44 will rise at a much faster rate due to the much greaterquantities of air being introduced into the separation and isolationchambers. This fact is used to advantage in the present invention bysetting the weight of the valve components at a value substantially lessthan the maximum amount of force which will be applied to the valvemember 124 to hold the valve shut due to the maximum pressuredifferential which can exist between the vacuum line and the interior ofthe chamber 44. This maximum pressure differential, which can approach30 inches of mercury, will not exist until after the water level hasreceded to a position below the lower globe 134 unless there is a majormalfunction of the system. In the latter instance, the pressure in thechamber 44 rises very rapidly e.g., in one or two seconds to a levelsuch that the pressure difference between the line 46 and the chamberinterior 44 will alone maintain the valve closed with- 7 out anyassistance from the b-uoyancy of the globe 132 or 13 4.

The latter feature of the invention has the advantage that when there isa major malfunction of the system, the valve will remain closed evenafter the water level has dropped below the lowest globe 134 and thechamber 44 has completely drained. This has the beneficial result thatabsolutely no water can pass into the vacuum line during majormalfunction of the wellpoint system. The valve 122 cannot be re-openeduntil either the vacuum pump 48 is turned off or the air valve 146 isopened to allow air to enter the vacuum line 46 from the atmosphere,thus breaking the vacuum hold on the valve 122. Since an operator mustperform either of these functions, he will have discovered the existenceof the major malfunction and will have either made the necessary repairsor shut down the equipment before resuming operation of the system.

As it can be seen from the foregoing, the valve 122 can be said to besensitive to the rate of pressure change in the chamber 44 to determineits operating cycle. That is, if, after the closing of the valve the gaspressure in the chamber increases at a rate greater than a certainpredetermined safe rate, the valve remains shut until the condition iscorrected. However, if the gas pressure in creases at a rate lower thanthe predetermined safe rate, the valve opens automatically when thewater level has receded to a satisfactorily low level in the chamber 44.

It should be evident that other forms of float mechanism can be usedwithout departing from the teachings of this invention. For example, asingle float can be used instead of the two separate globes 13 2 and134. Similarly, a separate weight need not be used if the weight of theother components is set at a level satisfactory for performance of thefunctions described above.

The vacuum pump 48 preferably is lubricated by recirculating oil. Theoil is circulated through a heat exchanger which uses clean water,preferably water which is being pumped in the pumping unit '18, to coolthe oil as it flows through the heat exchanger. By this means, thetemperature of the vacuum pump is maintained at a safe level, forexample, from around 150 to around 180 F.

The above description of the invention is intended to be illustrativeand not limiting. Various changes or modifications in the embodimentsdescribed may occur to those skilled in the art and these can be madewithout departing from the spirit or scope of the invention as set forthin the claims.

I claim:

1. A control method for a system for pumping dispersed liquids from theground, said system including a separation chamber connected withevacuation means for withdrawing gases from said chamber and from aliquid being pumped by said system, valve means selectively operable forclosing the connection between said chamber and said evacuation means inresponse to the rise of said liquid in said chamber to a predeterminedlevel, and drain means for draining said liquid from said chamber, saidmethod comprising closing said valve means in response to the rise ofsaid liquid in said chamber to said predetermined level, maintainingsaid valve means in a closed condition when, after the closing of saidvalve means, the gas pressure in said chamber is above a predeterminedvalue, and opening said valve means when, after the closing of saidvalve, said gas pressure is below said predetermined value and the levelof liquid in said chamber is substantially below said predeterminedlevel.

2. A method as in claim 1 in which said valve means is a float valvehaving a float member, and in which the closing of said valve meansincludes the step of applying to said valve means a closing force havinga buoyancy component developed by the buoyancy of said float in saidliquid, and a pressure component developed by the pressure differentialbetween said chamber and said evacuation means.

3. A method as in claim 2 in which the opening of said valve meansincludes the step of applying an opening force to said valve means, andin which said opening force is a gravitational force provided by theweight of said valve means.

4. A method as in claim 3 including the step of maintaining the weightof said valve means at a valve substantially less than the maximumpossible value of said pressure component of said closing force.

5. A method as in claim 2 including the steps of causing said buoyancycomponent to decrease at a rate substantially greater than the rate atwhich said pressure component increases during normal operation of saidpumping device after the closing of said valve means, and causing saidbuoyancy component to decrease at a rate substantially lower than therate at which said pressure component increases during periods after thevalve closes when abnormally large amounts of air are entering theseparation chamber.

6. In or for a system for removing dispersed water from the ground bymeans of a plurality of pipes extending into the ground at separatelocations, each of said pipes having at least one liquid inlet openingadjacent its lower end, a liquid pump for producing sub-atmosphericliquid pumping pressures for lifting water out of the ground, mainconduit means for connecting said pipes to said liquid pump, and aseparation chamber connected to said main conduit means for receivinggas separated from said liquid before it reaches said liquid pump, theimprovement comprising; a second chamber connected to said separationchamber to receive gas therefrom, a gas vacuum pump connected to saidsecond chamber to remove gas therefrom, gas conduit means for conductinggas from said separation chamber into said second chamber and from saidsecond chamber to said vacuum pump, return conduit means forautomatically returning separated liquid from said second chamber tosaid main conduit means, a float valve in said second chamber forclosing the connection to said vacuum pump when the liquid level in saidsecond chamber rises above a predetermined level, means for movablymounting said float valve so that at least a component of its weighttends to pull the valve open, said weight component of said valve beingsubstantially less than the closing force on said valve which is exertedby a pressure difference of approximately 30 inches of mercury betweensaid vacuum pump and said second chamber.

7. Apparatus as in claim 6 including a vacuum conduit connecting saidvacuum pump to said second chamber, and manually operable vent meansbetween said valve means and said vacuum pump for venting said vacuumconduit to the atmosphere.

8. Apparatus as in claim 7 in which said return conduit means comprisesa pipe connecting said second chamber directly to said main conduitmeans.

9. In a wellpoint system including a plurality of wellpoints, a liquidpump, a first liquid conduit connecting said Wellpoints to said liquidpump, a first chamber atop of and communicating with said first liquidconduit, a second chamber adjacent said first chamber, a first gasconduit interconnecting said first and second chambers from a pointadjacent the top of said first chamber to a point spaced upwardly fromthe bottom of said second chamber, a second liquid conduit connectingsaid second chamber to said first liquid conduit at points adjacent thebottom of each of the latter, a second gas conduit connected at one endto said second chamber adjacent its top, a gas evacuation pump connectedto the other end of said second gas conduit, valve means in said secondchamber, said valve means comprising at least one float member, arelatively rigid conical valve member, a rigid rod connecting said valvemember to said float member, a frustro-conical valve seat at theentrance of said second gas conduit at the top of said second chamber,means for guiding the movement of said valve member upwardly toward anddownwardly away from said valve seat to close and open said valve inresponse to the rise and fall of said float in said chamber, the totalweight of 5 said float member, said valve member and said rod beingequal to the total upward force applied to said valve member due to -apredetermined difference in gas pressure between said second chamber andsaid second gas conduit when said valve is closed, said second liquidconduit having dimensions such that liquid drains from said secondchamber at a rate such that said valve remains closed after closing whensaid pressure difference reaches or exceeds said predetermined levelbefore the liquid level drops below said float member.

References Cited UNITED STATES PATENTS 2,275,500 3/1942 Broadhurst103-l13 2,768,704 10/1956 Cronkhite 55l68 X REUBEN FRIEDMAN, PrimalyExaminer.

w R. W. BURKS, Assistant Examiner.

US. Cl. X.R. 5 51 68

